1. Field of the Invention:
The invention relates to a fan wheel for high-temperature operation, especially in ovens, including a star-like or ray-like base plate having a central middle region, protrusions protruding substantially radially beyond the central middle region, axially drawn up blades disposed on the protrusions and a base plate surface with axially drawn up segments extending from the middle region into the vicinity of the protrusions. The invention also relates to a method for manufacturing the fan wheel.
In a known fan wheel with a substantially star-shaped base plate and axially pulled or drawn up blades on the radial protrusions, which taper largely to a point, an annular bead is impressed, or in other words axially pulled or drawn up, all around the axial opening in the central middle region, and from there ray-like radial beads extend into the region of the radial protrusions. The radial beads extend asymmetrically with respect to the contour of the aforementioned protrusions. Such fan wheels are made of thin sheet metal material. Tests especially in the high-temperature range have shown that even after a relatively short time in operation, the radial protrusions become more or less deformed, causing the fan output to drop and producing irritating running noise.
2. Summary of the Invention:
It is accordingly an object of the invention to provide a fan wheel and a method for manufacturing the same, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type and with which the fan wheel is improved in such a way that even under highly varying temperature conditions, an exact, constant geometry and balanced position of the fan wheel are preserved.
With the foregoing and other objects in view there is provided, in accordance with the invention, a fan wheel for high-temperature operation, comprising a star-like or ray-like base plate having: a central middle region; protrusions protruding substantially radially beyond the central middle region and having an outer contour; axially drawn up blades disposed on the protrusions; and a base plate surface with axially drawn up segments extending from the middle region into the vicinity of the protrusions; the segments including a central, annular segment and star-like or ray-like segments adjoining the central, annular segment and extending through the protrusions of the base plate substantially symmetrically with the outer contour.
With the objects of the invention in view, there is also provided a fan wheel for high-temperature operation, comprising a star-like or ray-like base plate having: an outer contour; a central middle region; protrusions protruding substantially radially beyond the central middle region; axially drawn up blades disposed on the protrusions; and a base plate surface with axially drawn up segments extending from the middle region into the vicinity of the protrusions; the segments including a central, annular segment and star-like or ray-like segments adjoining the central, annular segment, originating from the central, annular segment and following the outer contour of the base plate.
In accordance with another feature of the invention, the segments are constructed as shapings.
In accordance with a further feature of the invention, the segments are substantially flat shapings having surfaces being drawn up relative to the base plate.
In accordance with an added feature of the invention, the segments merge with one another and are parts of a common segment and preferably of a common shaping.
In accordance with an additional feature of the invention, the segments have an outer contour, and there are provided peripheral surfaces of at least approximately constant width being disposed between the outer contour of the protrusions and the outer contour of the segments.
In accordance with yet another feature of the invention, the segments have a ray-like region and a drawn up depth being decreased as seen radially outwardly toward the ray-like region.
In accordance with yet a further feature of the invention, the segments have ray-like regions and axially drawn up embossed surfaces being constructed as shapings and provided with additionally axially drawn up bulges preferably having a circular outline, in transitional regions between the central annular region and the ray-like regions.
In accordance with yet an added feature of the invention, the base plate has a middle region, the ray-like protrusions have a root region, and the segments include an annular, axially drawn up segment in the middle region of the base plate extending at least approximately as far as the root region of the ray-like protrusions and being adjoined continuously by the star-like or ray-like segments.
In accordance with yet an additional feature of the invention, there is provided a a surface coating, preferably a layer of enamel, being disposed on the base plate.
With the objects of the invention in view, there is additionally provided a method for manufacturing a high-temperature fan wheel, which comprises initially axially drawing shapings and optionally bulges from a flat, preferably metal blank and subsequently cutting away the contour of the base plate and bending the blades relative to the base plate.
The axially pulled or drawn up segments, which are preferably constructed as generally flat stampings or shapings, lend the base plate such dimensional stability and heat resistance, even under an extreme thermal load, for instance up to 500.degree. C. when used in pyrolytic self-cleaning ovens, that no alteration of the geometrical relationships takes place, the balanced state is preserved, and a running noise that remains constantly low is achieved. Especially because of the largely symmetrical contouring of the segments, for instance from the presence of a largely constant edge between the segments and the outer contour of the base plate, thermally dictated expansions of material cannot cause partial rejections. Due to these properties that promote dimensional stability, it becomes possible to use even relatively thin, preferably metal sheet material with a low thermal capacity without having to fear disadvantages in terms of concentricity. Due to the aforementioned dimensional stability, the possibility also readily exists of providing the fan wheel with a relatively easily broken coating, for instance a catalytically self-cleaning enamel coating. Not the least advantage is the fact that the fan wheel according to the invention is distinguished by low production costs.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a fan wheel and a method for manufacturing the same, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.